3. Results

3.1 Carcass features and information collected on site

The adult female weighed 3.62 kg, with a body length of 68.2 cm, tail length of 29.4 cm; the female kitten weighed 2.62 kg, with a body length of 60.3 cm and tail length of 27.2 cm. Compared with the kitten, the adult clearly showed worn palm pads, claws and a greater tooth wear (especially canine teeth) (Fig. 3a, b). Both the carcasses showed a severed cervical spine caused by a carnivore bite, with fracture in C3-C5 of CMC-1 (Fig. 3c, d), while the occipital bone was dislocated from C1 for CMC-2 (Fig. 3e, f). Other than these fatal injuries, no other health issue was detected. This suggested that the spinal injury was the cause of death.
The body of the female kitten (CMC-1) was found right beside the farm of a local herdswoman on 30 Jan 2019. She reported that in the night of 29 Jan, when she was driving the yak herd back, she saw her dog chase the cat into its hiding burrow and bark in front of it. In the next morning, she found the dead body of the cat beside its den and, later, her dog dragged the dead cat approximately 50 m away from its burrow (Fig. 1b). On 7 Feb, the body of the adult female was also found beside its hiding burrow and similar description was also collected for it (Fig. 1b). One local herdsman reported that, two days before, stray dogs chased the adult female not far from where the body was found on 7 Feb. Based on our camera trap monitoring since Sept. 2018, no wild predators in Gyatong capable of killing the cats (e.g., lynxes, wolves, bears) have been recorded in the area. Therefore, all the evidence suggested that free-ranging dogs were responsible for the death of both cats.

3.2 Free-ranging dogs survey

Overall, 15 valid questionnaires were collected in Gyatong. The survey and interview suggested that there were two kinds of free-ranging dogs in the area: unchained domestic dogs and homeless stray dogs. In total, 166 domestic dogs were recorded in the Gyatong Grassland. Among them, 27 domestic dogs and seven stray dogs were found roaming in the range of the Chinese mountain cats (Fig. 4).
With respect to the rearing methods for the domestic dogs, all the interviewees suggested that they would chain their dogs in the daytime when there was someone home. However, domestic dogs would be set free at night or when the owners left home. No dogs are vaccinated. No dog abandonment was reported. There were also no cases of hybridization between domestic dogs and stray dogs according to the herdsmen. All the interviewees suggested that the number of stray dogs were increasing in recent years. When being asked about the potential origin of stray dogs, the locals suspected that they wandered here from Sichuan province.
In terms of attitudes towards stray dogs, most local herdsmen claimed that they were unaware of stray dogs’ predation on wildlife, yet showed high tolerance of such behaviors when informed. They were not averse to the capture of stray dogs so long as the dogs were not killed on-site and the control measures had no effect on domestic dogs.

3.3 Genetic analysis of carcasses

Taxonomic status of the Chinese mountain cat is controversial and a recent genomic study suggested an alternatively classification as a subspecies (F. silvestris bieti ) in wildcat conspecifics (Yuet al. , 2021), which we followed in the genetic analysis.F. s. bieti , F. s. ornate and F. s. silvestris were separated into three distinct lineages, and F. catus and its wild ancestry F. s. lybica formed one more lineage in the mitochondrial phylogeny. Both our Chinese mountain cats and hybrid kitten samples were clustered in the lineage of F. catus +F. s. lybica (Fig. 5a). Genotyping of nuclear loci showed that seven of the eight autosomal loci and all the three X-chromosomal loci for CMC1 and CMC2 were homozygous F. s. bieti genotype, while only one locus was homozygous F. catus genotype (Table 1). Those results indicated that the vast majority of the genome in this cat family originates from the Chinese mountain cat. However, domestic cats are identified as at least one of their maternal predecessors. The genotype of CAT1 and CAT2 was 4 homozygous F. catus loci, 1 homozygous F. s. bieti locus and 3 heterozygous loci on autosome, and 2 homozygous F. catus loci and 1 homozygous F. s. bieti locus on X chromosome (Table 1). The Y loci of male CAT2 wasF. catus genotype. The genetic compositions of the two ancestral species are both considerable, as ~70% from the domestic cat and ~30% from the Chinese mountain cat. However, the fact that they have homozygous genotype from both ancestral species suggested that the hybridization in this pedigree had happened for multiple generations.